This application relates to a method of detecting residual ceramic core in a final gas turbine engine component.
Gas turbine engines are known and typically include a fan delivering air into a bypass duct as propulsion air and into a compressor as core airflow. The air is compressed in the compressor and delivered into a combustor where it is mixed with fuel and ignited. Products of the combustion pass downstream over turbine components driving them to rotate.
As can be appreciated, the turbine components become quite hot when exposed to the products of combustion. As such, it is known to supply cooling air to internal passages in the turbine components.
One way to form internal passages in the turbine engine component is through investment casting. In investment casting, a core is formed in a mold, typically out of a ceramic material. That core is then placed in another mold and wax is molded around the core. The waxed and captured core is then covered with more ceramic material, which builds up an outer layer of ceramic outwardly of the wax, otherwise known as a casting shell.
The wax is then melted away and the remaining casting shell is then placed into an investment casting furnace where a molten metal is poured into a casting shell and resultantly encapsulates the core. This then forms a metal component having complex internal cooling structure. The outer ceramic layer is then removed and the inner ceramic core is leached away. This leaves internal passages.
However, the leaching process is not always as efficient as would be desirable. In particular, in blind internal passages and internal cavities with circuitous paths, it is often the case that residual ceramic core material may remain. It can be difficult to distinguish such residual ceramic material as opposed to the material of the component. Such residual ceramic material can provide a blockage or restriction to airflow through cooling chambers, which is undesirable.
It has been proposed to include a material in the cavities after the leaching that can be viewed utilizing radiation evaluation, such as X-ray to identify residual ceramic.
Recently, the challenges on gas turbine engine components has increased dramatically and the shape and size of the cooling channels has become much more complex.